This relates generally to electronic devices with displays and, more particularly, to display driver circuitry for displays such as organic-light-emitting diode displays.
Electronic devices often include displays. For example, cellular telephones and portable computers include displays for presenting information to users.
Displays such as organic light-emitting diode displays have an array of display pixels based on light-emitting diodes. In this type of display, each display pixel includes a light-emitting diode and thin-film transistors for controlling application of a signal to the light-emitting diode to produce light.
An organic light-emitting diode display pixel includes a drive thin-film transistor connected to a data line via an access thin-film transistor. The access transistor may have a gate terminal that receives a scan signal via a corresponding scan line. Image data on the data line can be loaded into the display pixel by asserting the scan signal to turn on the access transistor. The display pixel includes a current source transistor that provides current to the organic light-emitting diode to produce light.
Transistors in an organic light-emitting diode display pixel may be subject to process, voltage, and temperature (PVT) variations. Due to such variations, transistor threshold voltages between different display pixels may vary. Variations in transistor threshold voltages can cause the display pixels to produce amounts of light that do not match a desired image. Compensation schemes are sometimes used to compensate for variations in threshold voltage. Such compensation schemes typically involve sampling operations that are performed within each pixel during normal display operations and thus increase the time required to display images.
It is within this context that the embodiments herein arise.